姓张的小子

使用JMagick压缩图片大小尺寸

Posted by eDWARD at 22:25

1. 我们经常需要实现图片上传的功能，但是光是上传图片可能还是远远不够的，我们必须对我们上传的图片进行处理，改变大小等等。JMagick是ImageMagick提供的一套使用Java调用ImageMagick的API接口，功能非常强大，下面介绍如果使用这个API处理图片的大小。引入JMagick需要的类库：

   import magick.ImageInfo;
   import magick.MagickException;
   import magick.MagickImage;
   

2. 我们需要把图片保存为两个尺寸，这里要提前定义两种常量：

   public static String SIZENAME_LARGE = "large";
   public static String SIZENAME_SMALL = "small";
   

3. 下面介绍如何使用JMagick，里面用到的ImageUtil稍后会介绍，FileUtil是操作文件的工具类，这里就暂时不介绍了：

   MagickImage source = ImageUtil.getMagickImage("image file name");
   Map map = processHead(source);
   System.out.ptineln(map.get(SIZENAME_LARGE));
   System.out.ptineln(map.get(SIZENAME_SMALL));
   

   ImageUtil.getMagickImage(byte[] byte)

   public static MagickImage getMagickImage(byte[] byte) throws MagickException {
     ImageInfo info = new ImageInfo();
     return new MagickImage(info, byte);
   }
   

   processHead(MagickImage source)

   private Map processHead(MagickImage source) throws Exception {
     MagickImage regulate = null;
     MagickImage large = null;
     MagickImage small = null;
   
     //保存图片的临时目录
     String tempPath = "....";
     //随即生成一个文件名，真是情况生成的目录可能更复杂
     String fn = FileUtil.getInstance().getRandName();
     String largeName = SIZENAME_LARGE + "_" + fn + ".jpg";
     String smallName = SIZENAME_SMALL + "_" + fn + ".jpg";
   
     try {
       //改变图片大小
       regulate = ImageUtil.regulate(source);
       large = ImageUtil.resizePhoto(regulate, tempPath + largeName, 500, 750);
       small = ImageUtil.resizePhoto(large, tempPath + smallName, 90, 120);
       byte[] largeByte = large.imageToBlob(new ImageInfo());
       byte[] smallByte = small.imageToBlob(new ImageInfo());
   
       //保存图片的目录
       String uploadPath = "....";
       //写文件到目录
       FileUtil.getInstance().writeFile(uploadPath + largeName, largeByte);
       FileUtil.getInstance().writeFile(uploadPath + smallName, smallByte);
   
       //返回图片地址
       Map map = new HashMap();
       map.put(SIZENAME_LARGE, "/" + dir + largeName);
       map.put(SIZENAME_SMALL, "/" + dir + smallName);
       return map;
     } catch (Exception e) {
       throw e;
     } finally {
       if (small != null)
         small.destroyImages();
       if (large != null)
         large.destroyImages();
       if (regulate != null)
         regulate.destroyImages();
       }
     }
   }
   

   ImageUtil.regulate(MagickImage source)

   public static MagickImage regulate(MagickImage source) throws MagickException {
     int width = (int) source.getDimension().getWidth();
     int height = (int) source.getDimension().getHeight();
     if ((height + 0.0) / width > 1.5) {
       MagickImage image = null;
       MagickImage scaled = null;
       try {
         int newHeight = (int) Math.round(width * 1.5);
         Rectangle rect = new Rectangle(0, (height - newHeight) / 2, width, newHeight);
         ImageInfo info = null;
         info = new ImageInfo();
   
         scaled = source.cropImage(rect);
         return scaled;
       } finally {
         if (source != null) {
           source.destroyImages();
         }
       }
     } else {
       return source;
     }
   }
   

   ImageUtil.resizePhoto(MagickImage source, String destPathName, int maxWidth, int maxHeight)

   public static MagickImage resizePhotoStep(MagickImage source, String destPathName, int maxWidth, int maxHeight) throws MagickException {
     int width = 0;
     int height = 0;
     boolean change = true;
     width = (int) source.getDimension().getWidth();
     height = (int) source.getDimension().getHeight();
     if (maxWidth > width && maxHeight > height) {
       change = false;
     } else {
       if (width > 0 && height > 0) {
         if (height / width > maxHeight / maxWidth) {
           width = width * maxHeight / height;
           height = maxHeight;
         } else {
           height = height * maxWidth / width;
           width = maxWidth;
         }
       }
     }
   
     MagickImage scaled = null;
     scaled = source.scaleImage(width, height);
     scaled.setFileName(destPathName);
     return scaled;
   }
   

   下次介绍打标签的方法。

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